Aggregate Quality Research Articles

The Effect of the Ratio of Fly Ash to Alkaline Activator and the Molarity of NaOH on the Mechanical Properties of Fly Ash-Based Aggregates

The global demand for aggregates has escalated, leading to a decline in the availability of quality natural aggregates. In response, the cold bond pelletization (CBP) process emerged in the early 2000s as a novel approach to artificial aggregate production, utilizing dry powdered fly ash. This method involves agglomerating fly ash particles at room temperature in an inclined rotating pan to form pellets. However, the abstract lacks clarity in elucidating the significance of this approach. Our study investigates the mechanical properties of aggregates produced through the CBP method via experimental laboratory methods, focusing on variations in the ratio of fly ash to alkaline activator (FA/AA) and the molarity of Sodium Hydroxide (NaOH). Notably, we found that an effective molarity of 15 resulted in the lowest Aggregate Impact Value (AIV) percentage, indicating improved mechanical properties. Furthermore, we observed fluctuations in AIV values across different FA/AA ratios and NaOH molarities, suggesting nuanced effects on aggregate quality. Our findings underscore the importance of optimizing parameters in the CBP process for enhanced aggregate performance.

Talent Allocation in European Football Leagues: Why Competitive Imbalance May be optimal?

Abstract Professional sports are part of the entertainment industry; as such, its business is developed based on the perceived interest in sporting events, which in turn depends on features like: the (i) degree of competitive balance that determines the uncertainty of the outcome; the (ii) concentration of gifted players in a team, whose interaction of talents on the field enhances the quality of the ‘product joint’ that is a sporting event; the (iii) joint aggregate quality of rival teams; the (iv) appeal of rivalries associated with fans’ feelings of empathy and loyalty; etc. This paper focusses on the first three points by modelling the success of team-sport competitions as the result of the overall quality, which encompasses more than the mere sum of individual talents. Sport economists and practitioners generally acknowledge that competitive balance must be fostered to protect uncertainty about the outcome and thus achieve greater interest in sport competitions by fans and the media. In this paper, we argue that certain degree of imbalance in allocation of talent between teams may be preferable – rather than a perfect competitive balance – to broaden the interest of fans on the sport events and, thus, maximise economic outcomes. The paper also examines the discrepancies across the main European football leagues in this regard.

Evaluation and treatment of rhinosinusitis with primary antibody deficiency in children: Evidence-based review with recommendations.

There is clear evidence that prevalence of primary antibody deficiency (PAD) is higher in children with chronic rhinosinusitis (CRS) than in the general population. The purpose of this multi-institutional and multidisciplinary evidence-based review with recommendations (EBRR) is to thoroughly review the literature on rhinosinusitis with PAD, summarize the existing evidence, and provide recommendations on the evaluation and management of rhinosinusitis in children with PAD. The PubMed, Embase, and Cochrane databases were systematically reviewed from inception through December 2023. Studies on the evaluation and management of rhinosinusitis in PAD patients were included. An iterative review process was utilized in accordance with EBRR guidelines. Levels of evidence and recommendations on the evaluation and management principles for PAD were generated. A total of 50 studies were included in this evidence-based review. These studies were evaluated on the incidence of PAD in rhinosinusitis patients, the incidence of rhinosinusitis in PAD patients, and on the different treatment modalities used and their outcome. The aggregate quality of evidence varied across the reviewed domains. Based on the currently available evidence, the incidence of PAD in children with recalcitrant CRS can be significantly elevated. Despite the presence of multiple studies addressing rhinosinusitis and PAD, the level of evidence supporting different treatment options continues to be lacking. Optimal management requires a multidisciplinary approach through collaboration with clinical immunology. There is need for higher level studies that compare different treatments in children with PAD and rhinosinusitis.

Rapid quality control for recycled coarse aggregates (RCA) streams: Multi-sensor integration for advanced contaminant detection

Recycling coarse aggregates from construction and demolition waste is essential for sustainable construction practices. However, the quality of recycled coarse aggregates (RCA) often fluctuates significantly, in contrast to the more stable quality of natural aggregates. Contaminants in RCA notably compromise its quality and usability. Therefore, automating the quality control of RCA is necessary for the recycling industry. This study introduces an industry-focused, innovative, and rapid quality control system that combines Laser-Induced Breakdown Spectroscopy (LIBS) with 3D scanning technologies to enhance the detection of contaminants in RCA streams. The system involves a synchronized application of LIBS for spectral analysis and 3D scanning for the physical characterization of different materials. Results reveal that the dependability of single-shot LIBS analysis has been enhanced, thus elevating the precision of contaminant detection. This improvement is achieved by accounting for the laser shot's angle of incidence and focal length adjustments. The introduced technology holds potential for application in the real-time examination of substantial volumes of RCA, facilitating a rapid and reliable quality control method. This rapid assessment technique delivers online data about the concentration of contaminants in RCA, including recycled fine aggregates, cement paste, bricks, foam, glass, gypsum, mineral fibers, plastics, and wood. This data is both essential and sufficient for choosing a cost-effective mortar recipe and guaranteeing the performance of the final concrete product in terms of strength and durability in construction projects. The system can monitor the quality of RCA flows at throughputs of 50 tons per hour per conveyor, characterizing approximately 4000 particles in every ton of RCA, in this way signaling the most critical contaminants at levels of less than 50 parts per million. With these characteristics, the system could also become relevant for other applications, such as characterizing mining waste or solid biofuels for power plants.

Effect of treatment types of recycled concrete aggregates on the properties of concrete

Reusing waste materials such as construction and demolition waste is an environmentally significant task. This article aims to improve the quality of recycled aggregates after the demolition of concrete structures. Two methods, mechanical cleaning and impregnation, were explored to enhance the quality of coarse aggregates. The findings indicate that mechanical cleaning is more effective than soaking in a sodium silicate solution. The compressive strength of concrete made with mechanically cleaned recycled aggregates was 2.3 times greater than that of concrete made with untreated rubble. Concrete with impregnated rubble had a compressive strength 1.1 times greater than that of concrete with untreated aggregates. Infrared spectroscopy was used to study the microstructure, revealing that the type of treatment does not influence the quantity of portlandite and ettringite in hydrated cement. However, the treatment of recycled aggregates alters the interaction in the gel portion of cement hydration products. Concrete with aggregates treated by sodium silicate has more aluminate components. Additionally, there is a shift of the bands assigned to Si-O stretching to higher wave numbers (from 995 cm–1 to 1088 cm–1), which can be attributed to the formation of calcium-silicate-hydrate gel with a lower calcium/silicon ratio.

Evaluation of Concrete Compressive Strength with Coral Stone as a Fine Aggregate Replacement

This study examines the effect of using coral stone as a substitute for fine aggregate on the compressive strength of concrete. Tests were conducted with varying coral stone replacement percentages ranging from 0% to 100%. The results showed that coral stone can enhance the compressive strength of concrete, with an optimal replacement level of 80%, resulting in a 21.16% increase compared to normal concrete. However, replacements above 80% led to a decline in compressive strength, particularly at the 100% replacement level, which showed a 9.37% reduction in strength compared to normal concrete. This decrease was caused by increased porosity, varying aggregate quality, and an imbalance in the water-cement ratio, which disrupted the hydration process and microstructure formation of the concrete. Based on these findings, coral stone can be an effective alternative to replace fine aggregate such as sand, but its use should be limited to 80% to maximize the strength improvement without reducing performance.

Enhancing Concrete Properties through Fly Ash Pelletized Aggregates and Fibre Reinforcement - A Review

This literature review examines recent studies in Lightweight Aggregate Concrete (LWAC), specifically focusing on utilizing fly ash pelletization and fibre reinforcement to enhance concrete properties. Fly ash, a by-product of coal combustion, has gathered attention because of its potential to be put forward as a critical component in creating lightweight aggregates. The process of pelletization, which involves forming fly ash into small, spherical pellets, has been shown to improve the mechanical properties of the resulting concrete. The process mainly includes the cold-bonded pelletization method, which consumes energy and is easy to use. The review gives fusion findings from various studies examining fly ash's role in producing lightweight aggregates and the impact of different additives and processes on the resulting material properties. Key insights reveal that incorporating silica fume, fly ash, and steel fibres remarkably improves concrete's compressive and bonding strengths. Additionally, the cold-bonded pelletization of fly ash and cement, especially when combined with Polypropylene (PP) and steel fibres, leads to enhanced aggregate properties, including strength, density, and water absorption. The review also highlights the importance of optimizing pelletization parameters and binder usage to improve the quality of lightweight aggregates and enhance the properties of concrete. Moreover, integrating hybrid fibres, such as carbon and polypropylene, enhances concrete's postpeak performance and flexibility. The findings suggest that these innovations in fly ash pelletization and fibre reinforcement improve mechanical performance and contribute to more sustainable and cost-effective concrete production. This review provides a comprehensive overview of the current state of research, offering insights into the future direction of LWAC development.

Feasibility Assessment of Mudstone Aggregate as an Alternative Material for Colored Asphalt Pavement in South Korea

Colored asphalt pavements have been implemented in South Korea to enhance visibility and lane distinction; however, color fading, accelerated deterioration, and increased pothole occurrence have been noticed. As a solution, alternative materials that can be used for the construction of colored asphalt pavements are being explored. This study evaluates the feasibility of using mudstone aggregate in constructing colored asphalt pavement in South Korea. Initially, aggregate quality tests were conducted on mudstone samples to assess their suitability compared to standard criteria. To enhance the visibility and color retention of colored asphalt, addition of pigment in the colored asphalt pavement mixture was considered and evaluated. The asphalt mixtures were evaluated for deformation, crack and viscoelastic properties using the Kim test, indirect tensile (IDT) strength test, and dynamic modulus test, respectively. Results showed that mudstone aggregate exceeded quality standards and the colored asphalt mixtures demonstrated superior deformation strength and crack resistance compared to typical SMA. However, the addition of pigment slightly reduced these properties. Overall, the findings suggest mudstone aggregate as a viable alternative for constructing colored asphalt pavements, offering potential improvements in durability and color retention.

Mesoscale modeling of recycled aggregate concrete: A parametric analysis of the quality and shape of aggregate

AbstractRecycled aggregate concrete (RAC) is a multi‐phase material, and it is meaningful to investigate the effect of the properties of each phase. However, a comprehensive parametric analysis of these properties is still lacking, which limits a full understanding of the behavior of RAC. This paper uses numerical mesoscale models and contributes to knowledge on this topic. It focuses on the effects of the quality and shape of aggregate since they are relevant to the behavior of concrete but have scarcely been studied for RAC. Their effects on the mechanical response and fracture behavior of RAC were analyzed based on a validated two‐dimensional numerical model. In addition, this paper also justified the choice of the range of the parameters as well as benchmarked the numerical results with the state‐of‐the‐art. The main findings of the paper are: (1) stiffer aggregates decrease the tensile (by up to 29%) and compressive strength of RAC (by up to 7%); (2) aggregate shape moderately influences these properties by up to 10% and 8%; (3) the modulus of elasticity of RAC is considerably influenced by the stiffness of the aggregates (15%), while it is almost unaffected by the shape of the aggregates; (4) both stiffer and elongated aggregates tend to cause micro‐cracking in the interface and premature failure of concrete.

An intelligent mix design system for sustainable concrete containing multi-source recycled aggregate

The source complexity of recycled aggregate (RA) generally leads to significant fluctuations in the aggregate quality, which brings difficulties in the mix design of the recycled aggregate concrete (RAC). In this study, machine-learning models were developed to predict the cubic compressive strength by collecting mix proportions data including aggregate properties. Then a carbon emission model considering carbon sequestration was established. Based on these models, optimization algorithms were employed to obtain the optimal mix proportions. The results indicate that the backpropagation neural network model optimized by genetic algorithms (GABP) demonstrates the best predictive capability. Furthermore, the GABP model exhibits the highest sensitivity towards cement strength and water absorption of recycled coarse aggregate (RCA). In addition, single-objective optimization achieves a carbon reduction of 61.8–68.4 %. In dual-objective optimization, when the optimized mix proportions exhibit a low level of carbon intensity, the cubic compressive strength of RAC exceeds 50 MPa. This suggests that more efficient and valuable utilization of RA in concrete can be achieved after mix proportion optimization.

Chemical Modifications of Recycled Concrete Aggregate

The necessity for environmental sustainability has prompted the utilization of recycled concrete aggregates (RCA) sourced from structural demolition sites for the production of recycled aggregate concrete (RAC). The primary element impacting the quality of recycled concrete aggregate (RCA) is the mortar paste that adheres to the natural aggregate (NA). The cement mortar adhered to recycled concrete aggregate exhibits higher porosity and water absorption levels, along with reduced strength compared to natural aggregate. These characteristics negatively impact both the mechanical properties and durability of fresh and hardened concrete incorporating recycled concrete aggregate. As a result, it is crucial to enhance the interface by improving the surface of the aggregate or by removing the mortar adhered to the NA. Methods for achieving this include surface modification of the aggregate or removing adhered paste from the natural aggregate (NA). This research includes treatment involving acidic solutions particularly hydrochloric acid (HCl), and sulphuric acid (H2SO4), for mortar layer removal from RCA, analyzing their impact on the mechanical properties of aggregates and durability of concrete incorporating RCA.

Quality Evaluation of Guidelines for the Diagnosis and Treatment of Liver Failure.

This study aimed to systematically assess the methodological quality and key recommendations of the guidelines for the diagnosis and treatment of liver failure (LF), furnishing constructive insights for guideline developers and equipping clinicians with evidence-based information to facilitate informed decision-making. Electronic databases and manual searches from January 2011 to August 2023. Two reviewers independently screened titles and abstracts, then full texts for eligibility. Fourteen guidelines were included. Two reviewers extracted data and checked by two others. Methodological quality of the guidelines was appraised using the Appraisal of Guidelines for Research and Evaluation II tool. Of the 14 guidelines, only the guidelines established by the Society of Critical Care Medicine and the American College of Gastroenterology (2023) achieved an aggregate quality score exceeding 60%, thereby meriting clinical recommendations. It emerged that there remains ample room for enhancement in the quality of the guidelines, particularly within the domains of stakeholder engagement, rigor, and applicability. Furthermore, an in-depth scrutiny of common recommendations and supporting evidence drawn from the 10 adult LF guidelines unveiled several key issues: controversy exists in the recommendation, the absence of supporting evidence and confusing use of evidence for recommendations, and a preference in evidence selection. There are high differences in methodological quality and recommendations among LF guidelines. Improving these existing problems and controversies will benefit existing clinical practice and will be an effective way for developers to upgrade the guidelines.

Tackling P3HT:Y‐Series Miscibility Through Advanced Processing for Tunable Aggregation

AbstractPolymer and small molecule blend thin films are of strong interest for organic electronics and particularly organic solar cells. The high miscibility in blends of ordinary P3HT and state‐of‐the‐art Y‐series non‐fullerene acceptors (NFAs) suppresses phase separation and aggregation challenging successful charge separation and transport. In a recent work, current‐induced doping (CID) is introduced, a method to precisely control the aggregation of Poly(3‐hexylthiophene) (P3HT) in solution. The highly ordered pre‐aggregation in solution is used here to control the P3HT aggregation in neat films and blends with Y12 (BTP‐4F‐12). This results in a 25‐fold increase in hole mobility in P3HT organic field‐effect transistor (OFET) devices and tunability of the P3HT aggregate quality in the presence of Y12 over large ranges. At the same time, particularly the Y12 long‐range ordering is heavily suppressed by increasing P3HT aggregation. However, solvent vapor annealing (SVA) leads to an extraordinarily high Y12 ordering, changes in the crystal orientation of Y12, and a further improvement of P3HT aggregation. A broad range of different degrees of aggregation of both materials can therefore be obtained in the final thin films solely by changing processing parameters without changing the composition of the material system.

Environmental impacts and performance assessment of recycled fine aggregate concrete.

Natural disasters and human demolition create vast amounts of construction and demolition waste (CDW), with a substantial portion being concrete waste. Managing this concrete waste is a daunting challenge for developing countries with limited resources, aiming to mitigate its harmful environmental effects. Therefore, the proposed approach involves using recycled fine aggregates (RFA) instead of fresh fine aggregates (FFA) in concrete, which aligns closely with achieving sustainable environmental objectives. Extensive laboratory tests were conducted to assess the effects of adding RFA to concrete. The influence of 0 to 100% RFA replacement and different curing times was investigated on compressive strength, tensile strength, resistance against chloride ion penetration and chemicals exposure, and quality of aggregates. So, around 30%, 35%, 20%, and 79% reductions in compression strength, tensile strength, modulus of elasticity, and workability were estimated when 100% RFA was used in recycled aggregate concrete (RAC). However, according to results analyses, the performance of RAC is reliable up to 50% of RFA in proposed conditions and mix design. In addition, major environmental impacts such as global warming potential, aquatic eutrophication, and aquatic acidification were reduced by 47%, 40%, and 18%, respectively, for concrete having 50% RFA than concrete having 100% FFA.

PENGUJIAN AKARAKTERISTIK PASIR PANTAI KABUPATEN KOLAKA SEBAGAI MATERIAL ALTERNATIF PEMBUATAN BETON (Pasir Pantai Kec. Tanggetada, Kec. Watubangga dan Kec. Toari)

The quality characteristics of the concrete produced are greatly influenced by the quality of the fine aggregate used as a structural component, because fine aggregate has a large influence on the volume of concrete. So, the use of beach sand as a construction material must meet the specified requirements. The aim of this research is to determine the characteristics of beach sand in 3 (three) sub-districts in Kolaka district, whether it can be used in making concrete or not. The research method used was a detailed experiment carried out at the Concrete Laboratory of Sembilanbelas November University Kolaka with samples of Tanggetada Beach Sand, Watubangga Beach Sand and Toari Beach Sand. The results of testing the characteristics of the three beach sands used were obtained by testing data that met the requirements specified in SNI 03-1971-1990, except for the sieve analysis examination at No. 50 for all sand locations and No. 100 for Tanggetada and Toari Beach sand locations. Meanwhile, the specific gravity and water absorption, bulk weight, water content and passing sieve No. 200 have met the specifications. From the results obtained, the use of Watubangga Beach Sand can be used as sand material for normal concrete construction.

Hybrid Environmentally Friendly Method for RCA Concrete Quality Improvement

AbstractResearch on concrete recycling has led to the discovery of many processes for recycled concrete aggregate (RCA) treatment, each with its pros and cons on quality improvement, resource requirements, or scalability. This study aimed to propose a technique that combines two methods (mechanical grinding and acidic soaking) for mortar removal and improves the quality of RCA so as to realize a zero-waste, highly efficient, few-hours-long single-step process which we call acid milling. A quantitative comparison of aggregate and final concrete quality has been performed between each separate method. The proposed method shows about 57% relative improvement of aggregate quality for water absorption and density, while the concrete experiment shows up to 10% relative improvement for the compressive and flexural strengths compared with the untreated RCA concrete. This study paves the way for an efficient and sustainable concrete recycling process to be applied on a large scale.

Research on power generation prediction of hydropower in river basin based on multi-head attention graph convolutional neural network

For the power generation prediction of traditional hydropower stations, most of them only use time series prediction and neglect to study the spatial topological relationship of hydropower stations in the river basin, so that it is difficult to fully explore the characteristic relationship of space power stations. In this paper, a research method for power generation prediction of hydropower in river basin hydropower stations based on multi-head attention map convolutional neural network is proposed. This method establishes a first-level node neighborhood feature map based on the spatial geographic distribution information of hydropower stations in the basin, and uses the method of graph convolution to carry out node feature mining and feature learning, so as to transform the power generation capacity evaluation problem of the hydropower station in the basin into the node prediction problem in the graph, which is different from the global normalization rule. the multi-head attention mechanism introduced further improves the information aggregation quality of the graph node, and uses the historical temperature, power generation, electricity price, unit status and other data of each hydropower station in the basin for training. The reasoning results show that the proposed method achieves higher accuracy than other schemes, and the power prediction method is conducive to the formulation of power plans of hydropower stations in the basin, and can also play a positive role in guiding the site selection of hydropower plants.

Modeling carbonation depth of recycled aggregate concrete containing chlorinated salts

The durability of recycled concrete is susceptible to degradation from both chloride salt attack and carbonation when exposed in service environment. The depth of carbonation in recycled concrete subject to chloride salt attack was studied here. This investigation assessed the effects of mineral admixture, replacement rate of recycled coarse aggregate, and quality of recycled coarse aggregate on the carbonation depth. The carbonation depth Recycled concrete was studied through accelerated simulated carbonation in the laboratory for 7d, 14d and 28d. Based on the results, the correlation analysis was conducted to investigate the relationship between depth of carbonation, mineral admixture, recycled coarse aggregate replacement rate, recycled coarse aggregate quality and the presence of chloride ions. The objective of this study was mainly to investigate the effect of internal chloride ions on the depth of carbonation of recycled concrete subjected to chloride salt attack. The study referred to previous academic research on carbonation in recycled concrete that had not been affected by chloride salts, and conducted a comparative analysis to identify the carbonation depth pattern in recycled concrete influenced by chloride salt exposure. The study discovered a negative correlation between the replacement rate of mineral admixture and recycled coarse aggregate and the carbonation resistance of concrete. Moreover, enhancing the quality of recycled coarse aggregate positively impacted the carbonation resistance of concrete. An improved model was developed that considers the effect of internal chloride salts on the carbonation depth of recycled concrete, in reference to the empirical prediction model presently available. The model demonstrated a high level of agreement with experimental outcomes, displaying an error range of between −4.32% and 8.27%. It enables an in-depth comprehension of the carbonation behavior of recycled aggregate concrete in an environment exposed to chloride salt attack. Based on the model, the service life of recycled concrete structures can be more accurately forecasted, which can provide a theoretical direction for enhancing the durability of engineering structure.

Investigation of the Possible Correlations between Specific Characteristics of Crushed Stone Aggregates

This study rigorously investigates the interdependencies among a suite of crushed stone aggregate characteristics to enhance material selection for infrastructure projects. Utilizing data from Colas Északkő Ltd. (andesite quarries), the authors explore the relationships between mechanical and geometrical properties, particularly focusing on the interplay between the flakiness index, shape index, Los Angeles abrasion, Micro-Deval wear, and methylene blue assessments. The presented analysis reveals an unexpectedly robust correlation between FI and SI, proposing a novel paradigm for evaluating grain shape. Notably, the relationship between Los Angeles abrasion and micro-Deval wear values, typically considered disparate, is re-examined, unveiling potential predictive capabilities for environmental wear, especially as indicated by magnesium sulfate soundness testing. Additionally, the current study delineates a significant correlation between methylene blue values and micro-Deval wear performance, highlighting the intrinsic mineralogical influences on aggregate durability. The implications of findings are twofold: they suggest a streamlined approach for aggregate quality assurance and offer strategic insights into the refinement of material selection processes, thereby promising to enhance the durability and service life of transportation infrastructure.

Carbonation of Recycled Concrete Aggregates for New Concrete and Concrete Fines to Make Cement-Free Hollow Blocks

Mineral carbonation provides a way to increase the recycling of concrete waste in added-value products, and contributes to the principles of the circular economy. At present, most concrete waste is still downcycled. The high water absorption of recycled concrete aggregates, among other factors, impedes their recycling in the concrete industry. The quality of coarse recycled concrete aggregates (RCA) can, however, be enhanced by carbonation. Even when starting with high-grade RCA obtained from a selective demolition process, the carbonation process can decrease the water absorption of the RCA to as low as 3.0%. Concrete with a 50% replacement rate of carbonated RCA can be produced without a significant compressive strength reduction. The research further shows that carbonation can be performed at atmospheric pressure and low CO2 concentrations (e.g., 10%). The recycled concrete fines (RCF, 0–4 mm) in combination with 25% stainless steel slag were used to make zero-cement hollow blocks (39 × 19 × 9 cm) by carbonation curing without using any hydraulic binder. The hollow blocks have a compressive strength of 15.4 MPa at the lab scale. Both technologies were demonstrated on a pilot scale. In both processes, CO2 is immobilized in the resulting construction product. The developed production processes use less primary raw materials and cause less greenhouse-gas emissions than the production of traditional concrete products.